3.Proceedings of the Academy of Natural Sciences of Philadelphia by Academy of Natural Sciences of Philadelphia (1883)"... the genus Bufo, which comprises about 80 species, having only about 4-5 Nearctic
specific representatives (if we exclude the 6-7 species found in the ..."

4.The Tailless Batrachians of Europe by George Albert Boulenger (1898)"FIG. 78. \ Open mouth of Bufo calamita. The genus Bufo, of which some 100 species
are known, has representatives in most parts of the world, ..."

5.The Frog Book: North American Toads and Frogs, with a Study of the Habits by Mary Cynthia Dickerson (1906)"The genus Bufo is lacking in the Australian region. Bufo is the only genus of
the family found in North America, but this genus has thirteen species and a ..."